To provide an advertisement distribution system allowing an advertisement client to expect advertisement effect to perform an advertisement request at ease, by allowing investigation of whether information distributed as advertisement information for a screen saver is actually browsed and used or not.

An advertisement distribution server distributing the advertisement information and a communication terminal on a user side receiving the advertisement information are connected via a network. The advertisement distribution server has: a means for distributing the advertisement information as the screen saver to the communication terminal; and a utilization monitoring means for monitoring whether or not the advertisement information as the screen saver received by the communication terminal is displayed and utilized at screen saver start time. The communication terminal has: a means for making the advertisement information as the screen saver distributed from the advertisement distribution server be displayed and utilized at the screen saver start time; and a means for transmitting information showing that the advertisement information as the screen saver is made to be displayed and utilized at the screen saver start time to the advertisement distribution server.